Wyoming______Agricultural Experiment Station Bulletin 912 • Species Fact Sheet March 1996
Alpine Grasshopper Melanoplus alpinus Scudder
Distribution and Habitat reported to feed on grasses. In Idaho, crop content The geographic range of the alpine grasshopper is examinations show it to feed evenly on forbs and located in northwestern North America. It inhabits the grasses; in Colorado, 69 percent of its diet is forbs and grass-forb meadows and parklands of the Rocky Mountains 18 percent grasses; in southern Wyoming, 77 percent and the Sierra Nevada Mountains. In the United States, forbs and 12 percent grasses; and in northern Wyoming, altitudes of its habitats range from 6,400 feet in Montana to 93 percent forbs and 7 percent grasses. 11,000 feet in Colorado. In Canada, the species lives not Direct observations of the grasshoppers feeding in only in mountain meadows and parklands but also in their natural habitat west of Laramie, Wyoming totaled foothill habitats as low as 3,200 feet. 13 bouts on Arenaria congesta,13onPoa spp., and 9 on Taraxacum laevigatum. Average times spent feeding on these plants were A. congesta, 3 minutes; Poa spp., 1.8 minutes; and T. laevigatum 1.8 minutes. These results suggest that A. congesta was the preferred food plant. In a northern Colorado mountain meadow, A. fendleri served as the chief food plant. Crops of the alpine grasshopper contained 35 percent of this plant on both 10 and 23 August 1967 (Table 1). The number of food items per crop is of importance to the nutrition of grasshoppers; laboratory tests have shown increased weight, survival, and egg production of individuals among several species of Melanoplus when fed more than one kind of food plant. Adults of the alpine grasshopper usually contain more than one species of host plant in their crops. Collected Geographic range of Melanoplus alpinus Scudder from a meadow of the Laramie range, males contained an average of 1.2 items and females 3.2 items. Collected Economic Importance from a meadow of the Big Horn Mountains, males The alpine grasshopper, a common resident of contained an average of 1.8 items and females 2.4 items. mountain meadows, has a history of low densities and no These differences between the sexes were statistically documented outbreaks. Researchers of the species consider significant. it to be a minor pest during some years and often a Dispersal and Migration beneficial insect due to its feeding on competing weeds and Possessing long wings and developed wing poisonous plants such as locoweed and lupine. Populations muscles, the alpine grasshopper is able to fly evasively in Wyoming meadows have ranged in density from less and to disperse. Within the center of its distribution in than 0.1 to 3.7 adults per square yard. Because the alpine the Big Horn Mountains of northern Wyoming, the grasshopper feeds readily on Idaho fescue, it is considered a species inhabits a high percentage of the available potentially competitive pest with livestock on summer montane meadows, which suggests effective dispersal. range, particularly during droughts when forage is in short Additional evidence for dispersal was the collection of supply. one adult male on 5 September 1995 in a Food Habits bunchgrass-sagebrush habitat lying at an altitude of 7,300 feet - a foothill locale atypical for the species. The alpine grasshopper feeds on both forbs and None of the species was collected in this site on 3 grasses, and will eat fungi and injured or dead arthropods. August 1995 nor in the previous year on 25 July 1994. About 26 species of forbs, 11 grasses, and 2 sedges are On the other hand, no adults have been found in known to be ingested. Preferred forbs include Arenaria grasshopper glaciers with other species that inhabit congesta, Arenaria fendleri, Astragalus adsurgens, Lupinus montane meadows, a fact suggesting that the alpine laxiflorus, Oxytropis campestris, Musineon tenuifolium, and grasshopper disperses primarily by short, low flights. Taraxacum laevigatum. Preferred grasses include Poa spp., When flushed, the adult alpine grasshopper appears Elymus lanceolatus, Festuca idahoensis, and Stipa more often to jump than to fly. Nymphs (instar V) and occidentalis. Over its geographic range the alpine adults jump from 4 inches to 3 feet at air temperatures grasshopper subsists on different diets. In Canada it is of 46° to 70°F. Adults fly short distances at
1 Common______Western Grasshoppers
Instar 1 Figures 1-5. Appearance of the five nymphal instars of Melanoplus alpinus - their sizes, structures, and color patterns. Notice progressive development of the wing pads. BL = body length, FL = hind femur length, AS = antennal segments number.
temperatures of 54° to 70°F. The flight is low and silent. 1. BL 4.5-5.2 mm FL 2.3-2.6 mm AS 13. Identification Instar 2 The alpine grasshopper is a medium-sized, long-winged species (Fig. 6 and 7). Head, thorax, and tegmen are usually gray but may range in color to shades of light tan. The venter and sides of the abdomen are cream colored. The dark dorsal stripe of the hind femur is continuous and may fill most of the medial area, often the stripe has a wedge-shaped mark dorsally in the middle; the lower medial area is pale gray or tan (Fig. 8). The upper marginal area is tan and 2. BL 5.1-7 mm FL 3.3-3.9 mm AS 15. marked by three black transverse bars. The hind tibia is green, blue, or pink. The male cercus is bifurcate, the Instar 3 dorsal arm is stubby and blunt, and the ventral arm is sharply pointed and both arms bend medially (Fig. 9). The smaller Melanoplus infantilis, which often resides alongside the alpine grasshopper in mountain meadows, has a similar bifurcate cercus, but the lower arm ends in a rounded blunt tip and does not bend toward the median (compare the two). The nymphs are identifiable by their color patterns, shape, and structures (Fig. 1-5). The early nymphs and 3. BL 8.1-9.2 mm FL 5-5.4 mm AS 17-18. some of the late nymphs are recognizable in the field by Instar 4 their green bodies, dark compound eyes, and prominent dark dorsal stripe of the hind femur. 1. Head with face nearly vertical and colored plain green, often tan in older instars; ridges of frontal costa and preocular ridges spotted brown; a black bar is present on the side of the head behind the compound eye. 2. Pronotal disk with dusky band, which is spotted brown and present on each side; the band continues onto the meso-and metanotum or the 4. BL 9.2-12 mm FL 6.6-7.7 mm AS 18-21. wing pads of older instars and to the end of the Instar 5 abdomen. The venter of the thorax and abdomen is green or pale tan, sometimes with pale brown spots. 3. The hind femur is green or tan and has a prominent dark dorsal stripe, often with a light dorsal wedge in the middle. The lower medial area and the lower marginal area are pale green or pale tan. The upper marginal area is green or tan. 4. Nymphs may change body color when they 5. BL 13-15 mm FL 8.4-10.3 mm AS 21-23. undergo metamorphosis. All specimens are green in instar I. In Instar II approximately 85
2 ______Pfadt: Alpine grasshopper, Melanoplus alpinus Scudder March 1996
Figures 6-10. Appearance of the adult male and female of Male Melanoplus alpinus, left hindleg of adult female, male cercus, and eggs and egg pod.
percent are green and 15 percent are cream or pale tan; in instars III and IV approximately 52 percent are green and 48 percent are cream or pale tan; in instar V approximately 20 percent are green and 80 6. BL 17.5-18.5 mm FL 10.7-11.2 mm AS 23-25. percent are tan. Female Hatching Before eggs of the alpine grasshopper will hatch, they require a long developmental period in the soil. A study of eggs laid in the Big Horn Mountains of Montana and Wyoming revealed that the majority of eggs (92 percent) required three years of development before hatching and a smaller number (8 percent), two years. None hatched in one year; the eggs laid in one summer were unable to hatch the following spring. The cause for the delay is 7. BL 20.5-24 mm FL 12-13.2 mm AS 22-24. unknown but may be due to both cold temperatures of Hindleg mountain soils and to an extended diapause of the embryos. In mountain meadows of Wyoming, eggs of the alpine grasshopper start hatching from early to late June. The precise time depends on seasonal temperatures that affect snow melt and the thawing and warming of the soil. The period of hatching is short, ranging from 6 to 17 days. Nymphal Development
In spite of cold night temperatures and frequent cold 8. Hindleg of female showing yellow wedge in dorsal rains in the mountain environment, nymphs of the alpine stripe. grasshopper develop rapidly to the adult stage. During the Cercus day in their meadow habitats, they bask in the warming rays of the sun and then at night they seek shelter in ground litter and crowns of grass insulating themselves from night air temperatures that range from 34° to 53°F. Nymphal periods have been found to last from 25 to 40 days. The shortest period of 25 days occurred in 1955 in a meadow lying at 9,800 feet in the Snowy Range west of Laramie, Wyoming. Daily scouting of the meadow revealed the first hatch of nymphs on June 21 and the first adult on July 16. In 1994 and 1995, slightly longer 9. End of male abdomen showing the cercus. nymphal periods of 35 and 38 days were found to occur in a Pole Mountain meadow east of Laramie (altitude 8,600 Eggs feet). In 1994, in a Big Horn Mountain meadow of northern Wyoming (altitude 8,200 feet), the nymphal period took 37 days. Both male and female alpine grasshoppers have five instars. Adults and Reproduction The alpine grasshopper reaches the adult stage by early July in the mountains of Wyoming . In 1994, adults were first discovered on July 8 in both northern and southern mountains. In the Snowy Range study meadow 10. Exposed eggs and egg pod. west of Laramie, Wyoming (altitude 9,800 feet), adults
3 Common______Western Grasshoppers Pfadt: Alpine grasshopper, Melanoplus alpinus Scudder March 1996 were first observed on 16 July 1955. The first observation on the ground. At night, the grasshoppers rest deep in of mating in this site was noted on August 12, and the first grass crowns or wedge themselves as much as 2 inches oviposition a week later. Females select bare ground below the soil surface alongside a rock or boulder. Two between clumps of grass to deposit groups of 8 to 12 eggs. hours after sunrise they emerge from their shelters and Although populations of adults dwindle through the begin to bask, resting horizontally on bare ground or on summer, residual individuals are still present in mid litter. They turn a side perpendicular to the rays of the sun September. These individuals continue to mate and and lower the associated hindleg, exposing the abdomen. presumably to deposit eggs. Because alpine grasshoppers In meadows of the Big Horn Mountains of northern retreat into shelters when weather becomes inclement, Wyoming, basking begins about 7:30 a.m. DST and may early frosts do not affect their survival. last for two to three hours. Feeding occurs in the forenoon The pods are 1 to 1 1/8 inches long and curved at the and again in the afternoon. During a feeding observation bottom so that the terminal section with eggs, 3/8 inch in a Big Horn Mountain meadow at 9:51 a.m. DST, an long, lies diagonally in the soil. Offwhite froth fills the top adult male sitting horizontally on the ground was seen to section of the pod; tan froth surrounds the eggs at the feed on a short green sprout from its tip to base. Adults bottom. Eggs are yellow or pale tan and 4.3 to 5.0 mm may remain inactive on the ground in sheltered spots for long (Fig. 10). long periods of time during the day and may not move Population Ecology unless disturbed by roving insects, wind, or rain. A second period of basking occurs in late afternoon. Then as The alpine grasshopper enjoys a high frequency of evening approaches and temperatures fall, the occurrence in mountain meadows of Wyoming. In the Big grasshoppers enter their nightime shelters. Horn mountains of northern Wyoming, 12 of 14 meadow sites (85 percent) surveyed in 1994 were inhabited by Table 1. Mean percent dry weight of food items in the resident populations. Densities were low in all crops of Melanoplus alpinus in northern Colorado, populations, ranging from less than 0.1 to 0.5 adult per Larimer County. (Adapted from Hansen and Ueckert, square yard. The highest density of adults ever recorded in 1970.) the Wyoming annual grasshopper survey (1988-94) was Item 8/10/67 8/23/67 3.7 adults per square yard in a meadow of the Big Horn Mountains (13 August 1991). The entire grasshopper Arenaria fendleri 34.9 34.7 assemblage living in this site numbered 16 adults per Astragalus spp. and Oxytropis lambertii 19.7 15.8 square yard. Densities of the six species were: Bruneria Penstemon sp. 3.2 0.5 brunnea, 5.7; M. alpinus, 3.7; M. bruneri, 2.4; M. Taraxacum offinale 2.1 0.8 borealis,2;Camnula pellucida,2;andChorthippus Antennaria parvifolia 2.1 0.5 curtipennis, 0.2. The study of the alpine grasshopper in Achillea lanulosa 2.1 0.0 the Snowy Range in 1954-55 revealed densities ranging Cryptantha virgata 2.1 0.0 from 0.4 to 0.9 adult per square yard. To date, no Erigeron spp. 2.1 0.0 irruptions of the alpine grasshopper have been observed Poa spp. 4.6 2.6 even in years favorable for outbreaks of M. borealis and Festuca idahoensis 2.1 9.5 M. bruneri. The requirement of alpine grasshopper eggs to Agropyron spp. 1.7 3.9 be in the soil for two to three years before hatching Muhlenbergia filiculmis 1.4 2.9 complicates the study of population ecology of this Danthonia parryi 0.3 3.9 species. Bouteloua gracilis 1.2 1.5 Arthropod parts 2.4 4.8 Daily Activity Fungi 10.2 8.3 The alpine grasshopper is a geophilous species Number Crops 23 40 resting, walking, feeding, and performing other activities
Selected References
Alexander, G. and J. R. Hilliard, Jr. 1969. Altitudinal and Hansen, R.M. and D.N. Ueckert. 1970. Dietary similarity of seasonal distribution of Orthoptera in the Rocky Mountains some primary consumers. Ecology 51: 640-648. of northern Colorado. Ecol. Monogr. 39: 385-431. Kreasky, J.B. 1960. Extended diapause in eggs of high-altitude Bergstrom, R.C. 1955. Life history of the grasshopper species of grasshoppers, and a note on food-plant preference Melanoplus alpinus Scudder. M.S. thesis, University of Melanoplus bruneri. Ann. Entomol. Soc. Am. 53: Wyoming, Laramie, WY. 436-438. Brusven, M.A. 1972. Differentiation and ecology of common Rentz, D.C. 1962. Melanoplus alpinus Scudder in California. Catantopinae and Cyrtacanthacridinae nymphs (Orthoptera: Pan-Pacific Entomol. 38: 167-168. Acrididae) of Idaho and adjacent areas. Melanderia 9: 1-31.
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